1. Field of the Invention
The present invention relates to centrifuge tubes. More particularly the present invention is an improvement in the cap structure for a centrifuge tube which includes a flat roughened surface to permit writing on the top of the cap.
2. Description of the Prior Art
The prior art of the present invention is illustrated in the drawings accompanying this specification and show a centrifuge tube employing the old type of cap structure. It has traditionally included an external recess on the top of the cap which is included for several purposes one of which is ease of manufacturing by reducing material thickness which has to solidify in the mold for quicker curing. The recess formed in the top of the cap also permits a savings in material required to manufacture the centrifuge tube. Further, the particular design provides a weakened resistance to the bending of that portion of cap which is inserted into the centrifuge tube as a stopper thereby permitting easier insertion of the cap into the top of the tube.
The problem with the prior art is that it has been impossible to conveniently write on a centrifuge tube in a consistent manner to identify it. The sides of the tube, which is made out of polypropylene, are inherently slick because of the properties of the material, and are sharply curved because of the small diameter of the tube, and as a result are difficult to write on. It has therefore always been necessary to include a label which is either adhesively stuck to the centrifuge tube or attached to it with a translucent adhesive tape.
If the tag is placed on the side of the tube, it can not be read in many cases without removing the tube from its holding rack or container. If the tag is not secured onto the side of the tube properly, the irregularity of the tag can make it difficult to insert or remove the tube from its holding rack or container. Tags glued to the tops or caps of the centrifuge tube are often torn off when the tube is opened. None of these tags prove to be a satisfactory solution to marking the tubes.